[x,y]= dsolve('Dx=2.439*x+333.5418*y+3.1701e+05','Dy= 0.0112*x','x(0)=0','y(0)=750','t');
t=0:0.01:20;
x=eval(x);
y=eval(y);
subplot(1,2,1)
plot(t,y,'r-');

subplot(1,2,2)
plot(t,x,'-');



